Total heat exchanger and ventilation system using the same

ABSTRACT

A total heat exchanger having a structure capable of achieving an enhancement in total heat efficiency, and a ventilation system using the total heat exchanger are disclosed. The total heat exchanger includes an air supply duct for guiding outdoor air to an indoor space, an air discharge duct for guiding indoor air to the outdoors, an air supply fan arranged at one side of the air supply duct, the air supply fan sucking the outdoor air, and supplying the sucked air to the indoor space, an air discharge fan arranged at one side of the air discharge duct, the air discharge fan sucking the indoor air, and discharging the sucked air to the outdoors, and a heat exchanging element arranged at a region where the indoor air and the outdoor air cross each other, the heat exchanging element heat-exchanging the indoor air with the outdoor air. The heat exchanging element has a shape causing the indoor air and the outdoor air to flow through the heat exchanging element while forming an acute angle with respect to each other.

This application claims the benefit of Korean Patent Application No.P2005-46326, filed on May 31, 2005, which is hereby incorporated byreference as if fully set forth herein.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a total heat exchanger and aventilation system using the same, and more particularly, to a totalheat exchanger which has an improved structure so as to have anincreased heat exchange area, thereby being capable of achieving anenhancement in total heat efficiency, and a ventilation system using thetotal heat exchanger.

2. Discussion of the Related Art

Generally, air present in a confined space, for example, an indoorspace, is gradually contaminated as time passes in accordance withrepeated respiration of living beings in the indoor space. Accordingly,it is necessary to frequently replace contaminated air in the indoorspace with fresh outdoor air. To this end, a ventilation system using atotal heat exchanger is typically used.

In particular, various ventilation systems are used in houses, largebuildings, and factories, in order to ventilate indoor spaces.Ventilation systems include an air supply fan for supplying outdoor airto an indoor space, an air discharge fan for discharging indoor air tothe outdoors, and a duct for guiding the outdoor air to the indoor spacewhile guiding the indoor air to the outdoors. Such a ventilation systemmay also include a total heat exchanger for recovering a part of thermalenergy contained in the indoor air discharged to the outdoors.

However, the total heat exchanger has the following problems.

First, the height of the total heat exchanger, which is installed in theinterior of a ceiling, is restricted because the ceiling is designed tohave a restricted thickness. For this reason, the height of a heatexchanging element built in the total heat exchanger to perform heatexchange between indoor air and outdoor air is restricted. As a result,the heat exchange area of the heat exchanging element is reduced,thereby causing the total heat efficiency of the total heat exchanger tobe relatively lowered.

Second, the flow rate of air passing through the heat exchanging elementis too high to enable the heat exchanging element to effectively performa desired heat exchanging operation. As a result, a degradation in theefficiency of the total heat exchanger occurs.

Third, there is a problem in that an increase in flow resistance occursbecause the flow directions of indoor air and outdoor air passingthrough the heat exchanging element are greatly varied.

SUMMARY OF THE INVENTION

Accordingly, the present invention is directed to a total heat exchangerand a ventilation system using the same that substantially obviate oneor more problems due to limitations and disadvantages of the relatedart.

An object of the present invention is to provide a total heat exchangerhaving an increased total heat efficiency, and a ventilation systemusing the total heat exchanger.

Another object of the present invention is to provide a total heatexchanger capable of achieving a reduction in flow resistance, and aventilation system using the total heat exchanger.

Additional advantages, objects, and features of the invention will beset forth in part in the description which follows and in part willbecome apparent to those having ordinary skill in the art uponexamination of the following or may be learned from practice of theinvention. The objectives and other advantages of the invention may berealized and attained by the structure particularly pointed out in thewritten description and claims hereof as well as the appended drawings.

To achieve these objects and other advantages and in accordance with thepurpose of the invention, as embodied and broadly described herein, atotal heat exchanger comprises: an air supply duct for guiding outdoorair to an indoor space; an air discharge duct for guiding indoor air tothe outdoors; at least one air supply fan arranged at one side of theair supply duct, the air supply fan sucking the outdoor air, andsupplying the sucked air to the indoor space; at least one air dischargefan arranged at one side of the air discharge duct, the air dischargefan sucking the indoor air, and discharging the sucked air to theoutdoors; and at least one heat exchanging element arranged at a regionwhere the indoor air and the outdoor air cross each other, the heatexchanging element heat-exchanging the indoor air with the outdoor air,wherein the heat exchanging element has a shape causing the indoor airand the outdoor air to flow through the heat exchanging element whileforming an acute angle from each other.

The heat exchanging element may have a cross-sectional height smallerthan a cross-sectional width of the heat exchanging element.

The heat exchanging element may have a substantially-polygonal crosssection.

The heat exchanging element may have a substantially-diamond crosssection.

The at least one heat exchanging element may comprise a plurality ofheat exchanging elements arranged in series in a flow direction of airin the total heat exchanger.

The heat exchanging elements may guide an air flow passing through theair supply duct and an air flow passing through the air discharge ductsuch that the air flows pass through the heat exchanging elements in azig-zag manner.

The total heat exchanger may further comprise an air-discharge-sidebypass passage branched from the air discharge duct, and adapted toguide the indoor air to be directly discharged to the outdoors by aforcible suction force of the air discharge fan, without passing throughthe heat exchanging element.

The total heat exchanger may further comprise an air-supply-side bypasspassage branched from the air supply duct, and adapted to guide theoutdoor air to be directly discharged to the indoor space by a forciblesuction force of the air supply fan, without passing through the heatexchanging element.

The total heat exchanger may further comprise a filter unit arranged inthe air supply duct, and adapted to remove foreign matter contained inthe outdoor air.

The air supply fan may include a rotating shaft extendingperpendicularly to a discharge direction of the outdoor air dischargedto the indoor space.

The at least one air supply fan may comprise a plurality of air supplyfans. In this case, the total heat exchanger may further comprise adual-axial motor for simultaneously driving the air supply fans.

The air discharge fan may include a rotating shaft extendingperpendicularly to a discharge direction of the indoor air discharged tothe outdoors.

The at least one air discharge fan may comprise a plurality of airdischarge fans. In this case, the total heat exchanger may furthercomprise a dual-axial motor for simultaneously driving the air dischargefans.

The total heat exchanger may further comprise an air supply chamber forstoring air discharged by the air supply fan, and an air dischargechamber for storing air discharged by the air discharge fan.

In another aspect of the present invention, a ventilation systemcomprises: an air supply duct for guiding outdoor air to an indoorspace; an air discharge duct for guiding indoor air to the outdoors; anair supply fan arranged at one side of the air supply duct, the airsupply fan sucking the outdoor air, and supplying the sucked air to theindoor space; an air discharge fan arranged at one side of the airdischarge duct, the air discharge fan sucking the indoor air, anddischarging the sucked air to the outdoors; a heat exchanging elementarranged at a region where the indoor air and the outdoor air cross eachother, the heat exchanging element heatexchanging the indoor air withthe outdoor air; a first extension duct including a first diffuser fordiffusing the outdoor air supplied from the air supply duct into theindoor space; and a second extension duct including a second diffuserspaced apart from the first diffuser by a predetermined distance,wherein the heat exchanging element has a shape causing the indoor airand the outdoor air to flow through the heat exchanging element whileforming an acute angle from each other.

The first extension duct may further include a first lower extensionduct for connecting the air supply duct to the indoor space, and a firstupper extension duct for connecting the air supply duct to the outdoors.

The second extension duct may further include a second lower extensionduct for connecting the air discharge duct to the indoor space, and asecond upper extension duct for connecting the air discharge duct to theoutdoors.

It is to be understood that both the foregoing general description andthe following detailed description of the present invention areexemplary and explanatory and are intended to provide furtherexplanation of the invention as claimed.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are included to provide a furtherunderstanding of the invention and are incorporated in and constitute apart of this application, illustrate embodiment(s) of the invention andtogether with the description serve to explain the principle of theinvention. In the drawings:

FIG. 1 is a schematic perspective view illustrating an inner structureof a total heat exchanger according to a first embodiment of the presentinvention;

FIG. 2 is a schematic sectional view illustrating the heat exchangingelement shown in FIG. 1 and air flows passing through the heatexchanging element;

FIG. 3A is a graph schematically depicting a temperature variationdepending on the flow lengths of indoor air and outdoor air during acooling operation for cooling an indoor space;

FIG. 3B is a graph schematically depicting a temperature variationdepending on the flow lengths of indoor air and outdoor air during aheating operation for heating an indoor space;

FIG. 4 is a schematic perspective view illustrating an inner structureof a total heat exchanger according to a second embodiment of thepresent invention;

FIG. 5 is a schematic sectional view illustrating the heat exchangingelement shown in FIG. 4 and air flows passing through the heatexchanging element;

FIG. 6 is a schematic perspective view illustrating an inner structureof a total heat exchanger according to a third embodiment of the presentinvention; and

FIG. 7 is a schematic view illustrating a ventilation system equippedwith a total heat exchanger according to the present invention.

DETAILED DESCRIPTION OF THE INVENTION

Reference will now be made in detail to the preferred embodiments of thepresent invention, examples of which are illustrated in the accompanyingdrawings. Wherever possible, the same reference numbers will be usedthroughout the drawings to refer to the same or like parts.

In FIGS. 1 to 7, solid line arrows A represent a flow of indoor air, andbroken line arrows B represent a flow of outdoor air.

FIG. 1 is a schematic perspective view illustrating an exemplaryembodiment of a total heat exchanger according to the present invention.FIG. 2 is a schematic sectional view illustrating a heat exchangingelement shown in FIG. 1. FIG. 3A is a graph schematically depicting atemperature variation depending on the flow lengths of indoor air andoutdoor air during a cooling operation for cooling an indoor space. FIG.3B is a graph schematically depicting a temperature variation dependingon the flow lengths of indoor air and outdoor air during a heatingoperation for heating an indoor space.

Hereinafter, a first embodiment of the total heat exchanger according tothe present invention will be described with reference to FIGS. 1 to 3B.

The total heat exchanger includes an air supply duct 10 for guidingoutdoor air to an indoor space, an air discharge duct 20 for guidingindoor air to the outdoors, and a heat exchanging element 50 a forheat-exchanging the indoor air with the outdoor air. The total heatexchanger may further include an air supply fan 13 for sucking theoutdoor air, and supplying the sucked air to the indoor space, and anair discharge fan 23 for sucking the indoor air, and discharging thesucked air to the outdoors.

The heat exchanging element 50 a is arranged at a region where anoutdoor air flow guided by the air supply duct 10 and an indoor air flowguided by the air discharge duct 20 cross each other. The heatexchanging element 50 a heat-exchanges the indoor air with the outdoorair through exchange of sensible heat using a temperature differencebetween the indoor air and outdoor air and exchange of latent heat usinga humidity difference between the indoor air and outdoor air.

In detail, a first heat exchanging passage (not shown) and a second heatexchanging passage (not shown), through which the indoor air and outdoorair pass, respectively, are formed in the heat exchanging element 50 a.The first and second heat exchanging passages are defined by a heatexchanging membrane (not shown) having excellent thermalcharacteristics.

Accordingly, when indoor air and outdoor air, which have temperature andhumidity differences, pass through the associated heat exchangingpassages, respectively, heat exchange occurs between the indoor air andoutdoor air via the heat exchanging membrane.

A filter (not shown) may be arranged at one side of the heat exchangingelement 50 a. The filter functions to filter air to remove foreignmatter contained in the air. The filter may be detachably coupled to theheat exchanging element 50 a.

An air supply duct inlet 11 is provided at one end of the air supplyduct 10. The air supply duct inlet 11 communicates with the outdoors. Anair supply duct outlet 12 is provided at the other end of the air supplyduct 10. The air supply duct outlet 12 communicates with the indoorspace. Similarly, an air discharge duct inlet 21 is provided at one endof the air discharge duct 20. The air discharge duct inlet 21communicates with the indoor space. An air discharge duct outlet 22 isprovided at the other end of the air discharge duct 20. The airdischarge duct outlet 22 communicates with the outdoors.

The air supply fan 13 is arranged in the air supply duct 10, to forciblysuck outdoor air from the outdoors, and to supply the sucked air to theindoor space. The air discharge fan 23 is arranged in the air dischargeduct 20, to forcibly suck contaminated air from the indoor space, and todischarge the sucked air to the outdoors.

Both the air supply fan 12 and the air discharge fan 23 are mounted inan air supply fan housing and an air discharge fan housing,respectively. Motors (not shown) are arranged at the front sides of theair supply fan housing and air discharge fan housing, respectively.

Operation of the ventilation system configured as described above willnow be described.

When electric power is applied to the air discharge fan 23, in order toventilate indoor air contaminated to a certain level, the indoor air isintroduced into the air discharge duct 20 through the air discharge ductinlet 21. The indoor air introduced in the air discharge duct 20 flowsacross the heat exchanging element 50 a in a diagonal direction of theheat exchanging element 50 a.

After flowing across the heat exchanging element 50 a, the indoor air isguided along the air discharge duct 20, and is then discharged to theoutdoors through the air discharge duct outlet 22. Simultaneously withthe above-described flow of the indoor air, outdoor air is introducedinto the air supply duct 10 through the air supply duct outlet 22. Theoutdoor air introduced in the air supply duct 10 flows across the heatexchanging element 50 a in a diagonal direction of the heat exchangingelement 50 a.

After flowing across the heat exchanging element 50 a, the outdoor airis guided along the air supply duct 10, and is then supplied to theindoor space through the air supply duct outlet 12. The indoor air andoutdoor air, which flow in the above-described manner, heat-exchangewhile flowing across the heat exchanging element 50 a. Thus, the outdoorair is supplied to the indoor space under the condition in which theoutdoor air is maintained at an appropriate temperature.

Meanwhile, the indoor air is discharged to the outdoors mainly via twoflow paths. That is, in association with a first flow path, the airintroduced into the air discharge duct 20 through the air discharge ductinlet 21 passes through a first air discharge duct guide hole 24, andheat-exchanges with the outdoor air introduced into the air supply duct20 via the air supply duct inlet 11, and is then discharged to theoutdoors. On the other hand, in association with a second flow path, theair introduced into the air discharge duct 20 through the air dischargeduct inlet 21 is directly discharged to the outdoors by the suctionforce of the air discharge fan 23, without passing through the heatexchanging element 50 a.

In association with the latter case, the total heat exchanger furtherincludes an air-discharge-side bypass passage 26 for guiding the indoorair to be directly discharged through the air discharge duct outlet 22.The indoor air introduced into the air discharge duct 20 through the airdischarge duct inlet 21 flows along the air-discharge-side bypasspassage 26 after passing through a second air discharge duct guide hole25, and is then discharged to the outdoors. A damper may be arranged atthe air discharge duct inlet 21, in order to guide the indoor air to theair-discharge-side bypass passage 26.

In accordance with the above-described configuration, it is possible toreduce pressure loss caused by the heat exchanging element by preventingthe indoor air and outdoor air from passing through the heat exchangingelement when the temperature and humidity differences between the indoorair and outdoor air is small, as in the spring and autumn seasons.Accordingly, the load applied to the fan can be reduced. As a result, itis possible to achieve a reduction in power consumption, and thus, toachieve saving of energy.

Meanwhile, the total heat efficiency of the total heat exchanger dependson how efficiently the heat exchanging element 50 a heat-exchanges theindoor air with the outdoor air. In order to obtain a desired total heatefficiency, accordingly, it is necessary to increase the cross-sectionalarea of the heat exchanging element 50 a. However, there is arestriction in increasing the vertical length of the heat exchangingelement 50 a, namely, the cross-sectional height of the heat exchangingelement 50 a, due to restrictions in the design of the construction inwhich the total heat exchanger is installed.

Thus, the improvement in the total heat efficiency of the heatexchanging element 50 a and the minimization of the cross-sectionalheight of the heat exchanging element 50 a are in opposition to eachother. However, the inventor found the fact that it is possible toincrease the cross-sectional area of the heat exchanging element 50 awithout increasing the cross-sectional height of the heating exchangingelement 50 a, for an enhancement in the total heat efficiency of thetotal heat exchanger.

In detail, in accordance with the present invention, the heat exchangingelement 50 a is configured to cause indoor and outdoor air flows passingthrough the heat exchanging element 50 a to form an acute angle θtherebetween. The heat exchanging element 50 a is also configured suchthat the cross-sectional width w of the heat exchanging element 50 a islarger than the cross-sectional height h of the heat exchanging element50 a. In this embodiment, the heat exchanging element 50 a has a diamondshape, as shown in FIG. 2.

Of course, the heat exchanging element 50 a may have othercross-sectional shapes. For example, the heat exchanging element 50 amay have a curved or polygonal cross-sectional shape. Furthermore, theheat exchanging element 50 a may have a cross-sectional shape havingboth a rectilinear portion and a curved portion.

When the cross-sectional width of the heat exchanging element 50 a islarger than the cross-sectional height of the heat exchanging element 50a, the flow length of air flowing through the heat exchanging element 50a is increased, and the flow rate of the air is reduced. Accordingly,the indoor air and outdoor air passing through the heat exchangingelement 50 a can more efficiently heat-exchange with each other.

In addition, when the cross-sectional width of the heat exchangingelement 50 a is larger than the cross-sectional height of the heatexchanging element 50 a, the variation in the directions of air flowspassing through the air supply duct and air discharge duct is reduced.As a result, flow resistances in the air supply duct and air dischargeduct are reduced.

Hereinafter, a variation in temperature depending on the length of theflow path defined in the heat exchanging element according to thepresent invention will be described with reference to FIGS. 3A and 3B.

In each of FIGS. 3A and 3B, “X” designates a temperature differencebetween the temperature of indoor air varying depending on the length ofthe flow path of a heat exchanging element, as depicted by a graph A andthe temperature of outdoor air varying depending on the length of theflow path of the heat exchanging element, as depicted by a graph B, inthe case in which the heating exchanging element has a conventionalstructure. In each of FIGS. 3A and 3B, “Y” designates a temperaturedifference between the temperature of indoor air varying depending onthe length of the flow path of a heat exchanging element, as depicted bythe graph A and the temperature of outdoor air varying depending on thelength of the flow path of the heat exchanging element, as depicted bythe graph B, in the case in which the heating exchanging element has astructure according to the present invention.

For an operation mode for cooling the indoor space, for example, in thesummer season, the temperature of indoor air to be cooled is set to berelatively lower than the temperature of outdoor air, as shown in FIG.3A. The difference between the indoor air temperature and the outdoorair temperature is reduced in accordance with heat exchange carried outby the heat exchanging element 50 a of the total heat exchanger. Theoutdoor air, which has a relatively high temperature, heat-exchangeswith the indoor air, which is discharged to the outdoors. As a result,the outdoor air is supplied to the indoor space in a state in which thetemperature of the outdoor air has been lowered below the temperature ofoutdoor air present in the outdoors.

Referring to FIG. 3A, it can be seen that, in the case of the heatexchanging element having a cross-sectional shape according to thepresent invention, more effective heat exchange is carried out.Accordingly, it is possible to further reduce the temperature differencebetween the outdoor air supplied to the indoor space and the indoor airdischarged to the outdoors, using the heat exchanging element accordingto the present invention.

For an operation mode for heating the indoor space, for example, in thewinter season, the temperature of indoor air to be heated is set to berelatively higher than the temperature of outdoor air, as shown in FIG.3B. Referring to FIG. 3B, it can be seen that, in the case of the heatexchanging element having a cross-sectional shape according to thepresent invention, more effective heat exchange is carried out, ascompared to the conventional heat exchanging element.

Although the total heat exchanger according to this embodiment has beendescribed as being installed in the interior of a ceiling, it may beinstalled at a side wall of a building.

Hereinafter, a second embodiment of the total heat exchanger accordingto the present invention will be described with reference to FIGS. 4 and5.

The basic configuration of the second embodiment of the total heatexchanger according to the present invention is identical to that of thefirst embodiment as described above. In the second embodiment, however,the total heat exchanger includes a plurality of heat exchangingelements 50 b arranged in series in a flow direction of air in the totalheat exchanger.

As described above, there is a restriction in increasing thecross-sectional height of a heat exchanging element due to restrictionsin the design of the construction in which the total heat exchanger isinstalled. When the heat exchanging elements 50 b are arranged in seriesin a flow direction of air in the total heat exchanger, it is possibleto achieve an enhancement in heat exchange efficiency without anincrease in the cross-sectional height of the heat exchanging elements50 b.

As shown in FIG. 4, air flowing in each of the air supply duct 10 andair discharge duct 20 passes through the heat exchanging elements 50 bin a zig-zag manner. Accordingly, the total heat exchanging area of theheat exchanging elements 50 b and the length of the path, along whichair flows, are increased.

In addition, the flow velocity of the air is gradually reduced as theair sequentially passes through the serially-arranged heat exchangingelements 50 b. Such a reduction in flow velocity provides advantageouseffects in terms of heat exchange. As a result, it is possible toenhance the total heat efficiency of the total heat exchanger by virtueof the increased total heat exchanging area and the reduced air flowvelocity.

Meanwhile, it is preferred that the heat exchanging elements bedetachably coupled to the total heat exchanger. By virtue of such adetachable structure, it is possible to achieve easy assembly anddisassembly of the heat exchanging elements.

The total heat exchanger also includes an air-discharge-side bypasspassage 26. When the temperature and humidity differences between theindoor space and the outdoors are small, as in the spring or autumnseason, indoor air is discharged to the outdoors via theair-discharge-side bypass passage 26 without passing through the heatexchanging elements 50 b. In this case, there is no pressure lossthrough the heat exchanging elements 50 b. Accordingly, it is possibleto reduce the load applied to the air discharge fan, and thus, to reducepower consumption.

Although not shown, the total heat exchanger may also include anair-supply-side bypass passage for allowing outdoor air to be directlyintroduced into the indoor space. In this case, a damper is arranged atone end of the air-supply-side bypass passage, in order to control flowof outdoor air through the air-supply-side bypass passage. Accordingly,when it is unnecessary to heat-exchange indoor air with outdoor air, theoutdoor air is guided to pass through the inlet of the air supply duct,and then to be directly introduced into the indoor space via theair-supply-side bypass passage.

The total heat exchanger may further include a filter unit (not shown)for filtering outdoor air flowing through the air supply duct, to removeforeign matter contained in the outdoor air. Accordingly, the outdoorair can be supplied to the indoor space in a clean state after passingthrough the filter unit.

The filter unit includes a dust-collecting filter which has a fiber matstructure, to collect foreign matter such as dust. The filter unit mayalso include an antibiotic filter for removing bacteria present in air,a photocatalytic collector for removing fine dust and volatile organiccompounds passing through the filter, a deodorizing filter fordeodorizing air, an anion generator, or a combination thereof.

Hereinafter, a third embodiment of the total heat exchanger according tothe present invention will be described with reference to FIG. 6.

In accordance with this embodiment, the total heat exchanger includes anair-supply-side fan-motor assembly 130 and an air-discharge-sidefan-motor assembly 230.

The air-supply-side fan-motor assembly 130 includes a plurality of airsupply fans 131 each having a rotating shaft extending perpendicularlyto the discharge direction of outdoor air. similarly, theair-discharge-side fan-motor assembly 230 includes a plurality of airdischarge fans 231 each having a rotating shaft extendingperpendicularly to the discharge direction of indoor air.

The air supply fans 131 are driven by a single dual-axial motor 132.Similarly, the air discharge fans 231 are driven by a single dual-axialmotor 232. Since the air supply fans 131 and air discharge fans 231 aredriven by the associated dual-axial motors 132 and 232, respectively, itis possible to produce an increase amount of air flow. In theillustrated case, the total heat exchanger includes two air supply fans131 and two air discharge fans 231.

The total heat exchanger also includes an air supply chamber 17 definedin the interior of the total heat exchanger at the side of the airsupply fans 131, and adapted to store air discharged by the air supplyfans 131, and an air discharge chamber 27 defined in the interior of thetotal heat exchanger at the side of the air discharge fans 231, andadapted to store air discharged by the air discharge fans 231. As theair supply chamber 17 and air discharge chamber 27 temporarily store airto be supplied and air to be discharged, respectively, air can flowuniformly through the air supply duct and air discharge duct.

Although the rotating shafts of the air supply fan 13 and air dischargefan 23 extend in directions identical to the discharge directions ofoutdoor air and indoor air, respectively, in the above-describedembodiments, the rotating shafts of the air supply fans 131 and airdischarge fans 231 extend perpendicularly to the discharge directions ofthe outdoor air and indoor air, respectively, in this embodiment.

Hereinafter, an exemplary embodiment of a ventilation system accordingto the present invention will be described with reference to FIG. 7.

The ventilation system according to this embodiment includes a totalheat exchanger 1000 which has the same configuration as that of one ofthe above-described total heat exchangers. The ventilation system alsoincludes a first extension duct 500 and a second extension duct 600. Thetotal heat exchanger 100 is arranged at a region where the first andsecond extension ducts 500 and 600 meet.

The first extension duct 500 includes a first lower extension duct 520for enabling the air supply duct of the total heat exchanger 1000 tocommunicate with the indoor space, a first upper extension duct 530 forenabling the air supply duct of the total heat exchanger 1000 tocommunicate with the outdoors, and a first diffuser 510 for diffusingoutdoor air supplied to the indoor space.

In detail, the first lower extension duct 520 is connected, at one endthereof, to the air supply duct of the total heat exchanger 1000, and isconnected, at the other end thereof, to the first diffuser 510 partiallyopened to the indoor space. Of course, the first diffuser 510 may becompletely opened to the indoor space.

The second extension duct 600 includes a second lower extension duct 620for enabling the air discharge duct of the total heat exchanger 1000 tocommunicate with the indoor space, a second upper extension duct 630 forenabling the air discharge duct of the total heat exchanger 1000 tocommunicate with the outdoors, and a second diffuser 610 for suckingindoor air into the second extension duct 600.

In detail, the second lower extension duct 620 is connected, at one endthereof, to the air discharge duct of the total heat exchanger 1000, andis connected, at the other end thereof, to the second diffuser 610partially opened to the indoor space. Of course, the second diffuser 610may be completely opened to the indoor space.

The second extension duct 600 functions to enable the air discharge ductof the total heat exchanger 1000 to communicate with the indoor space,and to enable the total heat exchanger 100 to communicate with theoutdoors. The second diffuser 610 is mounted to an end of the secondextension duct 600.

As the ventilation system having the above-described configuration usesthe total heat exchanger according to the present invention, theventilation system can maintain a high total heat efficiencyirrespective of the design of the construction in which the ventilationsystem is installed.

It will be apparent to those skilled in the art that variousmodifications and variations can be made in the present inventionwithout departing from the spirit or scope of the inventions. Thus, itis intended that the present invention covers the modifications andvariations of this invention provided they come within the scope of theappended claims and their equivalents.

1. A total heat exchanger comprising: an air supply duct for guiding outdoor air to an indoor space; an air discharge duct for guiding indoor air to the outdoors; at least one air supply fan arranged at one side of the air supply duct, the air supply fan sucking the outdoor air, and supplying the sucked air to the indoor space; at least one air discharge fan arranged at one side of the air discharge duct, the air discharge fan sucking the indoor air, and discharging the sucked air to the outdoors; and at least one heat exchanging element arranged at a region where the indoor air and the outdoor air cross each other, the heat exchanging element heat-exchanging the indoor air with the outdoor air, wherein the heat exchanging element has a shape causing the indoor air and the outdoor air to flow through the heat exchanging element while forming an acute angle with respect to each other.
 2. The total heat exchanger according to claim 1, wherein the heat exchanging element has a cross-sectional height smaller than a cross-sectional width of the heat exchanging element.
 3. The total heat exchanger according to claim 1, wherein the heat exchanging element has a substantially-polygonal cross section.
 4. The total heat exchanger according to claim 3, wherein the heat exchanging element has a substantially-diamond cross section.
 5. The total heat exchanger according to claim 1, wherein the at least one heat exchanging element comprises a plurality of heat exchanging elements arranged in series in a flow direction of air in the total heat exchanger.
 6. The total heat exchanger according to claim 5, wherein the heat exchanging elements guide an air flow passing through the air supply duct and an air flow passing through the air discharge duct such that the air flows pass through the heat exchanging elements in a zig-zag manner.
 7. The total heat exchanger according to claim 1, further comprising: an air-discharge-side bypass passage branched from the air discharge duct, and adapted to guide the indoor air to be directly discharged to the outdoors by a forcible suction force of the air discharge fan, without passing through the heat exchanging element.
 8. The total heat exchanger according to claim 1, further comprising: an air-supply-side bypass passage branched from the air supply duct, and adapted to guide the outdoor air to be directly discharged to the indoor space by a forcible suction force of the air supply fan, without passing through the heat exchanging element.
 9. The total heat exchanger according to claim 1, further comprising: a filter unit arranged in the air supply duct, and adapted to remove foreign matter contained in the outdoor air.
 10. The total heat exchanger according to claim 1, wherein the air supply fan includes a rotating shaft extending perpendicularly to a discharge direction of the outdoor air discharged to the indoor space.
 11. The total heat exchanger according to claim 10, wherein the at least one air supply fan comprises a plurality of air supply fans, further comprising: a dual-axial motor for simultaneously driving the air supply fans.
 12. The total heat exchanger according to claim 1, wherein the air discharge fan includes a rotating shaft extending perpendicularly to a discharge direction of the indoor air discharged to the outdoors.
 13. The total heat exchanger according to claim 12, wherein the at least one air discharge fan comprises a plurality of air discharge fans, further comprising: a dual-axial motor for simultaneously driving the air discharge fans.
 14. The total heat exchanger according to claim 1, further comprising: an air supply chamber for storing air discharged by the air supply fan; and an air discharge chamber for storing air discharged by the air discharge fan.
 15. A ventilation system comprising: an air supply duct for guiding outdoor air to an indoor space; an air discharge duct for guiding indoor air to the outdoors; an air supply fan arranged at one side of the air supply duct, the air supply fan sucking the outdoor air, and supplying the sucked air to the indoor space; an air discharge fan arranged at one side of the air discharge duct, the air discharge fan sucking the indoor air, and discharging the sucked air to the outdoors; a heat exchanging element arranged at a region where the indoor air and the outdoor air cross each other, the heat exchanging element heat-exchanging the indoor air with the outdoor air; a first extension duct including a first diffuser for diffusing the outdoor air supplied from the air supply duct into the indoor space; and a second extension duct including a second diffuser spaced apart from the first diffuser by a predetermined distance, wherein the heat exchanging element has a shape causing the indoor air and the outdoor air to flow through the heat exchanging element while forming an acute angle with respect to each other.
 16. The ventilation system according to claim 15, wherein the first extension duct further includes a lower extension duct for connecting the air supply duct to the indoor space, and an upper extension duct for connecting the air supply duct to the outdoors.
 17. The ventilation system according to claim 15, wherein the second extension duct further includes a lower extension duct for connecting the air discharge duct to the indoor space, and an upper extension duct for connecting the air discharge duct to the outdoors. 